Method of providing a fluid tight seal between two rigid components



NOV. 22, 1966 MQCORD METHOD OF PROVIDING A FLUID TIGHT SEAL BETWEEN TWORIGID COMPONENTS Original Filed March 21, 1963 INVENTOR.

GEORG E P. McCORD ATTORNEY United States Patent 3,287,485 METHOD OFPROVIDING A FLUID TIGHT SEAL BETWEEN TWO RIGID COMPONENTS Georgie P.McCord, Oaklandon, Ind., assignor to United States Rubber Company, NewYork, N.Y., a corporation of New Jersey Original application Mar. 21,1963, Ser. No. 266,922, now Patent No. 3,191,655, dated June 29, 1965.Divided and this application Sept. 19, 1963, Ser. No. 309,930 2 Claims.(Cl. 264-263) This application is a division of my copending applicationSerial No. 266,922, filed March 21, 1963, now Patent No. 3,191,655.

This invention relates to an article of manufacture wherein afluid-tight seal is provided between two rigid components throughcompression of an elastomeric component between the two rigid members,and to a method of making same. Potential applications of my inventionare fluid-tight closures and valves. More particularly, my inventionrelates to a valve stem assembly for a tubeless tire and rim and to amethod of making the same.

The principal object of my invention is to provide a novel method ofmaking a new and improved article having a fluid-tight seal between tworigid members. Another object is to provide a method of fabricating animproved tubeless tire valve. Another object is to achieve the foregoingobjects using conventional molding equipment and in particular, aninjection molding process. Numerous other objects will appearhereinafter.

In one broad aspect, my invention is a method of making an article ofmanufacture comprising a first rigid component, a second rigidcomponent, one of said rigid components being composed of solid plastic,one of said rigid components surrounding the other, and an elastomericcomponent disposed between the rigid components and being compressedtightly therebetween and forming a fluid-tight seal between the tworigid components.

In another broad aspect, my invention is a method of obtaining afluid-tight seal between two rigid components which comprises insertingone of said rigid components (which can be composed of wood, metal,plastic, ceramic, artificial stone or any other suitable rigid materialdepending upon the end use of the finished article) and a curedelastomeric, but compressible, component in a mold cavity with one ofthe rigid components and the elastomeric component in contact with eachother and with one surrounding the other and with an empty spaceconstituting part of the mold cavity in annular contacting relationshipwith the elastomeric component, injecting plastic material, capable ofsetting to a rigid condition at room temperature, into the empty spaceuntil it has filled the same and has caused the elastomeric component tobe tightly compressed against the first rigid component, and causing theplastic material so injected to set to form the second rigid component,after which the article is removed from the mold.

In practicing my invention, compression of the rubber component to formthe fluid-tight seal is obtained by using the rubber component and oneof the rigid components as inserts in a plastic injection mold andapplying the other rigid component as a plastic component by injectionmolding.

The use of rigid inserts in injection molding of plastic articles iscommonplace, but the use of elastic as opposed to rigid inserts is tothe best of my knowledge novel and in particular the injection of aplastic to compress an elastic insert and thereby efifect a fluid-tightseal between two rigid inserts is novel. The end use of the articleemploying my fluid-tight seal will dictate the choice of materials.Thus, the rubber part may have to be compounded for oilorweather-resistance, non-toxicity or for any number of otherqualifications. Any elastomer,

3,287,485 Patented Nov. 22, 1966 which is deformable under compressionbut is resilient so that it will rapidly resume its original shape uponremoval of the deforming force, is a prospective material. Examples ofrubbers which can be used are: SBR, butyl, butadiene-acrylonitrilerubber (so-called Buna N or nitrile rubber), neoprene, natural rubber,cis-l,4-polybutadiene, synthetic cis-polyisoprene, ethylene-propylenerubber, ethylene-propylene-diene rubber, etc. The rigid component thatis injection molded to complete the fluid-tight seal must of necessitybe a plastic material. The first consideration is that it must be amaterial that will not yield (or flow) under the compression forceexerted by the rubber component in the finished article and thereby failto maintain a fluid-tight seal. In addition it is selected to haveproperties adapted to the environment in which it will be used.

I will now describe my invention with particular reference to thefabrication of a tubeless tire valve.

Tubeless tire valve stem assemblies have been fabricated from rubber andplastic components in an effort to achieve manufacturing economies. Sucha valve stem assembly has been disclosed in my US. Patent No. 3,032,-091. These valves achieve economies not only by utilizing inexpensivematerials, but also by eliminating the costly machining necessary withthe use of conventional metal parts.

In one specific application, the instant invention provides a tubelesstire valve assembly comprising a resilient rubber sealing member havingan outside diameter greater than the diameter of the valve stem openingin the rim, the inner end of the rubber member being inserted in theopening so that the rubber is compressed into sealing engagementtherewith. The inner end of the rubber member is defined herein as thatend extending into the air chamber defined by the rim, the outer endbeing that which is exposed. The rubber member has an axiallyextendingcylindrical recess passing therethrough and is also provided with atleast one protruding element on the exterior surface of its outer end.

A rigid tubular member, which may be of plastic, is disposed within thiscylindrical recess, the tubular member itself being adapted to receive avalve core therein. The tubular member is also provided with aprotruding element on its exterior surface adjacent the outer end of therubber member. In use a valve core is disposed in the outer end of thetubular member.

Finally, a molded plastic sleeve surrounds both the rubber member andthe tubular member, the interior surface of the sleeve conforming to theprotruding elements on the exterior surfaces of the rubber member andthe tubular member. Thus, the sleeve locks the two members together influid-tight realtionship.

Conveniently, the protruding element on the exterior surface of therubber member may desirably comprise a circumferentially extending rib.Likewise, the protruding element on the exterior surface of the tubularmember may desirably comprise a circumferentially extending projectingflange. This flange is adapted to seat itself on the outer end of therubber member.

The invention also contemplates a method of making such a tire valveassembly. The method comprises assembling a resilient rubber sealingmember having an outside diaineter greater than the diameter of theopening in the tubeless tire rim, an axially extending cylindricalrecess passing therethrough, and at least one protruding element on theexterior surface of the outer end, with a rigid plastic tubular memberin the cylindrical recess.

The tubular member is provided with a protruding element on its exteriorsurface adjacent the outer end of the rubber member and is also adaptedto receive a valve core therein. The assembly is placed in a mold havinga cavity portion surrounding both the rubber member and the tubularmember, the cavity portion including the protruding elements on theexterior surfaces of the rubber member and the tubular member. Finally,plastic material is injected into the cavity portion of the mold underpressure, thereby to lock the rubber member and the tubular membertogether in fluid-tight relationship.

The invention will be further understood by referring to the followingdescription, when read in conjunction with the accompanying drawings,wherein:

FIG. 1 is an enlarged plan view of the valve stem assembly of theinstant invention;

FIG. 2 is a cross-sectional view taken on line 22 of FIG. 1;

FIG. 3 is an exploded cross-sectional view of the resilient rubbersealing member and the rigid. plastic tubular member; and

FIG. 4 is a cross-sectional view showing the rubber member and thetubular member assembled in a mold cavity preparatory to injectingplastic material into the cavity portion of the mold to lock the memberstogether.

Referring to the drawings and in particular to FIGS. 1, 2 and 3, thevalve of the instant invention, generally designated by reference 10, iscomprised of a resilient rubber sealing member 12 assembled with a rigidplastic inner tubular member 11 and locked together by means of a moldedplastic sleeve 13.

The resilient rubber sealing member 12 can be conveniently made bystandard compression molding methods and is provided with an outsidediameter greater than the diameter of the opening in the tubeless tirerim. Thus, a conventional rim engaging groove 18 and dome 19 constitutethe rim sealing portion of valve 10. Rubber member 12 is molded with anaxially extending cylindrical recess 12a therethrough and is alsoequipped with a series of alternate circumferential grooves and ribs 17,to facilitate the locking of members 11 and 12 together. The type ofrubber stock used in rubber member 12 is not limited by the particularvalve design, but rather is dictated by the end use of the valve.

The plastic tubular member 11 shown in detail in FIG. 3 is convenientlymade by standard injection molding methods. The choice of plastic is notparticularly limited other than by the consideration of physicalproperties. Thermoplastics such as nylon or thermosetting plastics suchas Bakelite (a phenol-formaldehyde resin) may be used. Tubular member 11is provided with a seat 14 for engagement with rubber member 12. Member11 is also provided with a circumferentially extending projecttypes ofvalves, such as the one disclosed in the aforementioned Patent No.3,032,091, may also be used.

As shown in FIG. 2, the rubber member 12 and tubular member 11 arelocked together in fluid-tight relationship by a molded plastic sleeve13. Sleeve 13 surrounds rubber member 12 and tubular member 11 as shown.The interior surface of sleeve 13 conforms to the protruding elements onthe exterior surfaces of the other members.

The valve is made by assemblying members 11 and 12 so that tubularmember 11 is received within cylindrical recess 12a of rubber member 12until seat 14 comes into engagement with member 12. The assembly is thenplaced on a pin 20 on a mold plate 21. As shown in FIG.

4, an upper mold 22, having a preformed cavity 23, is

:then clamped in place and plastic material is injected into the cavityportion 24 through sprue 25, thus to form sleeve 13. The injectionpressure, relative to the plastic material being injected, creates acompressive force on rubber member 12, thereby sealing members 11 and12in air-tight engagement.

Example Rubber component 12 is made by the usual compression moldingmethod commonly used in the industry, using either of the followingformulations:

SBR compound: Parts by weight SBR (butadiene-styrene rubbery copolymer)100 Butyl compound: I

Butyl 150 (a commercial type of butyl rubber) 100 ZnO 85 Medium channeltype Carbon Black 30 Hydrocarbon oil 10 Tetramethyl thiuram disulfide(accelerator) 1 Mercaptobenzothiazole (accelerator) 1 Sulfur 4 The abovecompounds are mixed on conventional rubber mills and vulcanized undercompression in a mold approximately 13 minutes at 350 F.

The rigid tubular insert 11 must be sufficiently inflexible orunyielding to resist deformation from forces resulting from theinjection molding operation used to form the locking piece 13, and tothen maintain compression on the rubber insert 12 in the finished part.materials which meet this requirement and are otherwise suitable are:metals, e.g., brass; thermosetting plastics such as polyester-styrenemixtures, phenol-formaldehyde resins, melamine-formaldehyde resins,urea-formaldehyde resins, etc.; thermoplastics such as nylon,polyethylene, polypropylene, cellulose acetate, methyl methacrylatepolymer (so-called acrylic polymer), polystyrene, polyvinyl chloride,polyvinyl acetate, so-called graft polymers, blends of graft polymerswith styrene-acrylonitrile resins, blends of Buna N withstyrene-acrylonitrile resins, etc. Rubber is not applicable except ashard rubber or so-called ebonite.

The locking piece 13 is generally made from a thermoplastic materialcapable of being injection molded. Thermosetting plastics have notgenerally been found to be adapted to be injection molded. Examples ofsuitable materials and their molding temperatures and pressures are asfollows:

The selection of suitable materials for the two rigid inserts and forthe elastorneric insert and of suitable methods of fabricating each ofthese three elements including the determination of mold design, of amethod of locating members 11 and 12 in the mold, and of injectionpressure and temperature for the injection molding step will be obviousto those skilled in the art from this description.

Examples of.

The instant invention results in reduced costs because of thesubstitution of plastic materials for metals. Also, the cost ofinjection molding of plastic is less than the cost of machining metal.Finally, the method of assembling the valve is cheaper than that of theconventional valve with a metal insert, inasmuch as no chemicalpreparation of the metal is required in order to insure a proper metalto rubber bond.

While a particular embodiment of the invention has been shown anddescribed, it is to be understood that this is for the purpose ofillustration only and that changes and modificatioins can be madetherein without departing from the spirit and scope of the invention.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. The method of obtaining a fluid-tight seal between two rigidcomponents, comprising positioning a first rigid component and a curedelastomeric component in a mold cavity in annular contactingrelationship one with the other and With an empty space constitutingpart of said mold cavity in annular contacting relationship with saidelastomeric component,

injecting plastic material, capable of setting to a rigid condition atroom temperature, into said empty space until it has filled same and hascaused said elastomeric component to be tightly compressed against saidfirst rigid component, and

causing the plastic material so injected to set to form the second rigidcomponent.

2. The method of making a tire valve for use in a tubeless tire rimhaving a valve stem opening therethrough, comprising assembling aresilient rubber sealing member having an outer diameter greater thanthe diameter of said opening in said rim,

an axially extending cylindrical recess passing therethrough, and atleast one protruding element on the exterior surface of its outer end,with a rigid tubular member in said cylindrical recess,

said tubular member being provided with a protruding element on itsexterior surface adjacent the outer end of said rubber member, saidtubular member being adapted to receive a valve core therein; placingthe assembly in a mold having a cavity portion surrounding said rubbermember and said tubular member,

said cavity portion including said protruding elements on the exteriorsurfaces of said rubber member and said tubular member; and injectingplastic material into said cavity portion under pressure, thereby tolock said rubber member and said tubular member together in fluid-tightrelationship.

References Cited by the Examiner UNITED STATES PATENTS 2,218,639 10/1940Crowley 264248 X 2,275,081 3/ 1942 Maynard 264-248 X 2,329,346 9/1943Gofi 264-248 X 2,409,759 10/1946 Hosking 264271 X 2,939,906 6/1960Harwood 264263 X 3,100,641 8/1963 Nicholls et al. 264-275 X ROBERT F.WHITE, Primary Examiner.

L. S. SQUIRES, Assistant Examiner.

1. THE METHOD OF OBTAINING A FLUID-TIGHT SEAL BETWEEN TWO RIGIDCOMPONENTS, COMPRISING POSITIONING A FIRST RIGID COMPONENT AND A CUREDELASTOMERIC COMPONENT IN A MOLD CAVITY IN ANNULAR CONTACTING RELATIONSIPONE WITH THE OTHER AND WITH AN EMPTY SPACE CONSTITUTING PART OF SAIDMOLD CAVITY IN ANNULAR CONTACTING RELATIONSHIP WITH SAID ELASTOMERICCOMPONENT, INJECTING PLASTIC MATERIAL, CAPABLE OF SETTING TO A RIGIDCONDITION AT ROOM TEMPERATURE, INTO SAID EMPTY SPACE UNTIL IT HAS FILLEDSAME AND HAS CAUSED SAID ELASTOMERIC COMPONENT TO BE TIGHTLY COMPRESSEDAGAINST SAID FIRST RIGID COMPONENT, AND CAUSING THE PLASTIC MATERIAL SOINJECTED TO SET TO FORM THE SECOND RIGID COMPONENT.